The present invention relates generally to systems for removing human wastes from a sump associated with a toilet bowl by vacuum pressure and rinsing it thereafter, and more particularly to such a system entailing a differential pressure-operated discharge valve, water valve, and controller valve, as well as a holding sump and vacuum source, which are completely portable.
In a conventional portable toilet system, such as a portable toilet structure commonly known as a PORTA-JOHN.RTM., the toilet seat is mounted directly on top of a holding sump. Human waste drops directly into the sump by means of gravity, where it is collected for subsequent purification and treatment. While such toilet systems are simple in design, and easy to install and operate at construction sites, roadside rest stops, popular outdoor events, etc., they are frequently unsanitary and subject to offensive odors, and usually do not provide a wash sink. For a typical person, they are used as a last resort.
The airplane industry has long felt the need for a more sanitary and appealing toilet system for its aircraft, featuring a conventional toilet bowl and a wash sink. Because of the ready source of vacuum pressure provided by high altitude environments, differential pressure has been used to operate such systems instead of positive pressure provided by a pump. Thus, U.S. Pat. No. 3,922,730 issued to Kemper discloses a recirculating toilet system for use in aircraft or the like. Waste from the toilet bowl is discharged along with a volume of water into a holding sump having a screen positioned therein for separating liquid from the solid elements of the waste stream by means of gravity. While the solid fraction is removed from the sump and therefore the aircraft by means of the differential pressure caused by the reduced pressure condition outside the aircraft, the liquid fraction is chemically treated and then pumped back to the toilet bowl for purposes of rinsing it during a subsequent flush cycle. However, a simple diaphragm actuated flapper is used as a discharge valve, and the control means for regulating the discharge of the contents of the toilet bowl to the holding sump and ejection of rinse water into the toilet bowl are completely electro-mechanical in nature (i.e., a solenoid valve). A vacuum-operated portable toilet system, such as that taught by Kemper, is complicated in design, and its costs are justifiable only in terms of the production and operational costs of the aircraft, itself.
U.S. Pat. No. 4,199,828 issued to Hellers discloses a vacuum toilet apparatus for portable units like trains or buses. Waste in the toilet bowl is discharged under the influence of a vacuum pressure into a material sluice having a simple flap valve at the bottom end thereof. Once a sufficient volume of waste material and liquid is accumulated therein, its weight opens the flap valve and is discharged into a storage tank by means of gravity for subsequent treatment. The vacuum pressure is provided by compressed air passing through a pneumatic ejector. Liquid from a container is discharged into the toilet bowl to rinse it. However, not only does the Hellers system require a source of compressed air to operate the pneumatic ejector, but also the volume of vacuum pressure created thereby is typically small. Moreover, electronic control means are required to operate the system.
U.S. Pat. No. 3,995,328 issued to Carolan et al. discloses the vacuum toilet system that is currently used on Boeing-built aircraft. Although once again the differential pressure between the aircraft cabin pressure and ambient conditions at high altitudes is used while the plane is in flight, a vacuum pressure transducer operated by means of pumps provides a vacuum pressure source, while the aircraft is on the ground to draw material from the toilet bowl and wash basin into the holding sump. A filter in the holding sump is used to recover sufficient liquid from the waste matter so that the liquid may be recycled as the flushing fluid for rinsing the toilet bowl. But the design of the flush and rinse valves are not disclosed, and the control means for the system is primarily electronic.